Should Torsion Balance Technique Continue to be Taught to Pharmacy Students?

INTRODUCTION

Compounding, in this era of personalized medicine, is a crucial skill for pharmacists, the only health care professionals educated in the art and science of compounding. Recently, there has been a call for greater emphasis on uniformity and quality control in compounding. This emphasis should begin at its foundation, the education that pharmacists receive while they are in school. But instruction in compounding, including the underlying science and math, has declined over the years in part because of the inclusion of clinical coursework and experiential training.¹ The Accreditation Council of Pharmacy Education (ACPE) continues to list extemporaneous compounding as a required component of any accredited pharmacy curriculum across the United States,² yet there is no national standardized compounding education curriculum. Unfortunately, some educators now place less priority on teaching extemporaneous compounding. The 2012 AACP Task Force on the status of compounding in education reported a range from 0 to 6 semesters of compounding education across US pharmacy schools that provided a response.³ It is not surprising that some pharmacists report they do not compound because of their lack of appropriate training.^4,5

Prioritization of compounding education across pharmacy schools is clearly needed as the number of compounded prescriptions continues to grow. The 2012 AACP Task Force on the status of compounding in education supports compounding in the curriculum, with a hands-on laboratory and associated equipment and supplies.³ A 2005 survey of pharmacists in independent pharmacies (in Illinois, Missouri, Kansas, and Iowa) found 94% of respondent pharmacies provided compounding services and that 2.3% of prescriptions dispensed were for compounded medications.⁴ The International Academy of Compounding Pharmacists (IACP) reports that 1% to 3% of the prescriptions filled in the United States are for compounded prescriptions.⁶ With 4 billion prescriptions of all types filled annually,⁷ this translates into millions of compounded prescriptions being prepared each year. The National Community Pharmacist Association (NCPA) estimates from 30 million to 40 million prescriptions for compounded medications are filled annually.⁸ A recently published study that reviewed insurance claims in 2012 and 2013 found the prevalence of compound users increased from 1.1% to 1.4% over the study period, an increase of 27.3%.⁹ Additionally, membership has reached 3900 for the Professional Compounding Centers of America (PCCA),¹⁰ and 4000 for the International Association of Compounding Pharmacists (IACP).¹¹ According to the Compounding Pharmacies Market Research Report March 2016,¹² the compounding industry has grown due in large part to manufacturer drug shortages and the aging population. This growth is expected to accelerate over the next five years.¹²

Preparation of prescriptions that are accurate is emphasized within the AACP 2016 Standards.² Accuracy in compounding is a fundamental skill of competent pharmacists. This includes accuracy in calculations, procedures, and all measurements, including weighing. Compounding requires the use of a precise and accurate balance to achieve therapeutic efficacy and safety for the patient. In USP Chapter <1176>, “Prescription Balances and Volumetric Apparatus, a prescription balance is defined as “a scale or balance adapted to weighing medicinal and other substances required in prescriptions or in other pharmaceutical compounding.”¹³ A “Class A” (typically referred to as class III)¹⁴ balance should be used for all the weighing operations required in prescription compounding. The sensitivity requirement or limit of a Class A balance is defined as a pointer shift of not less than one index-scale division when 6 mg has been added to a pan. The chapter does allow for balances such as micro-, semi-micro-, or electronic single-pan balances to be used provided they possess equivalent or better accuracy. Chapter <1251> goes on to discuss the operational and performance qualifications of an analytical balance in terms of linearity, eccentricity, sensitivity, and repeatability.¹⁵ The gold standard has been to avoid errors of > 5%, although a few studies in pharmacy schools suggested that 10% may be a more realistic expectation.^16,17 Repeatability and accuracy are elaborated under Chapter <41> (balances).¹⁸ Of course, accuracy is dependent upon how well the balance has been maintained. The USP does not specify when or how performance qualifications should be completed, just that all equipment must be routinely inspected, calibrated as necessary and documented per standard operating procedures of the pharmacy.^13,15,18,19 Missouri Department of Agriculture, Weights, Measures and Consumer Protection only certifies commercial weighing and measuring devices.²⁰

Historically, torsion balances have been utilized in pharmacies to weigh ingredients. Hence, the torsion balance has been the sole balance utilized in the Introduction to Pharmacy Practice and Pharmaceutics laboratories at St. Louis College of Pharmacy (STLCOP). Torsion balances are relatively easy to use, durable, and accurate but require several steps in terms of equilibration, adding weight, and using the release knob each time the substance to be weighed is increased or decreased. This process can be time-consuming and can potentially lead to errors. Students spend considerable time learning how to properly use torsion balances but have expressed concerns verbally and on laboratory evaluations that this type of balance has become obsolete and are not as accurate as digital balances. This perception interferes with the level of student attentiveness during laboratory training and adversely affects student learning.

In recent years, digital balances have become increasingly popular because of their ease of use and speed of operation. Fewer steps in the weighing process should result in fewer errors and lesser time requirement. In addition, the price of a good digital balance has decreased substantially over recent years, making these balances very attractive, especially in pharmacies that compound a significant number of prescriptions. Both types of balances are considered accurate if used correctly, though their readability and sensitivity differ. Newton discussed the weighing accuracy of torsion balances as compared to digital balances. According to Newton’s report, the sensitivity of torsion balances are 0.006g, and the smallest readable amount is 0.01g, whereas electronic balances can range from 0.01g to 0.002g.²¹ A study by Kadi and colleagues compared a solution prepared by students using a torsion balance and a digital balance. There was no statistical difference in the magnitude of the error of the unacceptable formulas (p>.05) and no difference in accuracy of the acceptable formulations.²²

In an effort to support current practice in pharmacy and to guide educational efforts as part of the Pharmaceutics laboratory, the Pharmaceutics team at STLCOP decided to investigate whether torsion balances continue to be the primary balance used in Missouri to compound prescriptions. The State Board of Pharmacy in Missouri does not require pharmacies to own a specific type of balance (2016 search of the Missouri code of state regulations 20CSR 2220-2.010).²³ Similar statutes are found in other states, such as Texas²⁴ and Oregon.²⁵ In some states, such as Wisconsin,²⁶ Virginia,²⁷ and Illinois,²⁸ all pharmacies must have a balance, but the type of balance is not specifically indicated. Because balances are not required, the actual numbers of torsion balances in Missouri pharmacies and the extent of their use in compounding are largely unknown. Therefore, the objective of this study was to determine the types of balances (torsion or digital) used in compounding pharmacies in Missouri via a survey in 2014.

DISCUSSION

Extemporaneous compounding has long been a skill practiced by pharmacists that sets them apart from all other health care professionals. It is expected that each and every prescription is prepared with the highest degree of accuracy, and the full responsibility for the compounded preparations is held by the pharmacist. Faculty at STLCOP are in agreement concerning the importance of compounding education. To guide educational efforts in compounding as part of the Pharmaceutics course laboratory, an investigation of the types of balances (torsion or digital) used in Missouri pharmacies was conducted via a mailed survey to registered pharmacies in Missouri in 2014.

In this study, data was collected regarding the current use of torsion balances in compounding across Missouri. The results of this study indicate that torsion balances remain integral to current compounding practice in Missouri with significantly more pharmacies solely owning a torsion balance versus those solely owning a digital one. Because a literature search revealed no other study on this subject, a comparison to other studies cannot be made. However, an explanation for the difference in the type of balance owned might be because of the prior Missouri law that required a balance in all pharmacies. Torsion balances were historically the type of balances found and utilized in pharmacies. Pharmacists may not be aware that the law has changed and therefore would have them present, especially if they were still in use. Additional reasons for the presence of torsion balances include pharmacist preferences, comfort level for use of a torsion balance, and the potentially prohibitive cost of digital balances if compound prescription volume is relatively small. There are several advantages to using a torsion balance: they are less messy and easier to physically use than some digital balances when weighing semi-solids and liquids as need arises; require less maintenance; can be used in a power outage; do not require a warm-up period; require less frequent calibration compared to digital balances; and have long durability and functionality if properly maintained.

The study population is representative of pharmacies in Missouri as well as nationwide. The percent of those pharmacies that self-identified as one of the three major practice sites in this study (independent, chain, hospital) reflects the percent of Missouri registered pharmacies in 2014. There are 16 pharmacy categories in Missouri, but only one community pharmacy classification, which includes both independent and chain pharmacies.³¹ In Missouri, there were 87.8% community pharmacies, and 8.2% hospital pharmacies registered in 2014, which is quite similar to the results reported herein. The practice site breakdown is also similar to that reported by the NCPA 2015 Digest³² of 2014 community pharmacy data. Of a total of 1150 community pharmacies in Missouri, 42% were reported as independent pharmacies, and 58% as either traditional chain, mass merchant or supermarket. Of the 303 community pharmacies in this study, 47% self-identified as independent, and 53% as chain community pharmacies.

Although the survey data was found to be representative of Missouri as discussed above, the study population that was surveyed also constitutes a limitation. Because more than 50% of the students enrolled at STLCOP are from Missouri, the survey exclusively targeted pharmacies registered with the Missouri Board of Pharmacy. By limiting the study to Missouri, no definitive comment can be made on the prevalence of using torsion balances nationwide. However, the findings in this study are likely reflective of many other states as well given the distinct differences in terms of population densities among the surveyed eight Missouri regions as well as the compound user demographics and differences in practice site composition compared to nationwide statistics. A recent study⁹ on compounded medications in insured patients reported that the national average for prevalence of compound users was 1.4%, with Missouri’s prevalence reported as 1.5% to 1.7%. Hence, the Missouri data is comparable to the data reported nationwide. The breakdown of community practice sites in the study reported herein is similar to what is observed nationwide. The NCPA 2015 digest reported 37% as independent pharmacies, and 63% as either traditional chain, mass merchant or supermarket, which is comparable to the findings discussed herein.³²

Pharmacists were also queried on their view of torsion balance instruction. Their opinion is important because they are the ones who are responsible for prescription compounding and are knowledgeable about pharmacy needs and demands. The majority of pharmacists who participated in this survey [59.7% of all respondents, whether they owned or used a balance or not] advocated for the continuation of torsion balance instruction. As expected, the majority of pharmacies that exclusively owned and used torsion balances advocated for their continued instruction. Similarly, the pharmacists at pharmacies that do not own a balance advocated for continued torsion balance instruction. An explanation for these results could be that these pharmacists are aware of the prevalence of torsion balances in pharmacies and, therefore, pharmacists should know how to use them. Surprisingly, pharmacists who exclusively use a digital balance to compound were almost equally divided in advocating for torsion balance instruction.